Magnetic printer



Sept. 18, 1956 J. c. SIMS, JR

MAGNETIC PRINTER Filed May 11, 1955 FIG. I.

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21 Q' r [Q INVENTOR. JOHN C. SIMS, JR.

BY (M a? 2:

AGENT United States Patent MAGNETIC PRINTER John C. Sims, Jr., Springhouse, Pa., assignor, by mesne assignments, to Sperry Rand Corporation, New York, N. Y., a corporation of Delaware Application May 11, 1955, Serial No. 507,641 16 Claims. (Cl. 101-119) The present invention relates to printing and printing devices, and is more particularly concerned with a method and apparatus for effecting printing by utilizing magnetic principles. In this respect, the present invention is primarily concerned with printers in the nature of mimeograph machines, utilizing rotatable printing cylinders; and especially relates to such printing devices wherein a porous or grid-type printing cylinder selectively permits or inhibits the flow of an ink to an external surface of such a cylinder.

A number of mimeograph-type devices are known wherein membranes are employed which allow the selective passage of a marking fluid to a receiving surface by noninhibition of some areas of a semi-porous membrane to render corresponding areas of the receiving surface of one opacity, and by the selective inhibition of such marking fluid through other areas of such a semi-porous membrane, thereby to render other corresponding areas of the said receiving surface of a second opacity.

In conventional mimeograph-type devices, such membranes or stencils are ordinarily mechanically produced by an embosser in standard typewriters or electrical stencil cutting machines, and such stencils or embossed membranes are then transferred to printing equipment adapted to permit ink flow through porous portions of the membrane so as to produce the foregoing marking of a receiving medium. Other types of devices are known wherein porous cylinders are employed for the selective passage of marking fluid or inks therethrough, and certain of these other forms of mimeograph devices rely upon the provision of selective electrostatic or electromagnetic control of the marking fluid. Thus, prior devices, such as are exemplified in I-Iuebner Patents 2,224,391, 2,408,- 144, 2,547,706, and 2,635,534, rely upon the provision of electromagnetic control of a marking fluid through a porous membrane or stencil.

In general, such known devices are characterized by the provision of a porous printing cylinder or stencil cooperating with auxiliary pull-out magnets, for selectively attracting or repelling magnetic inks through a semiporous membrane. These pull-out magnets often comprise auxiliary drums mounted adjacent an ink feeding drum, whereby the overall device is relatively bulky and expensive to manufacture; and in addition, raise serious problems of maintenance.

The present invention serves to obviate these difficulties, and provides a printing device in the nature of a mimeograph, utilizing a porous membrane or porous printing cylinder containing, internally thereof, an ink or marking fluid exhibiting magnetic properties. The membrane, stencil, or printing cylinder is further characterized by the provision of an external surface having a magnetic coating adapted to receive and store a pattern of magnetic gradients representative of information to be printed; and this stored pattern of gradients, comprising a latent image, cooperates with the aforementioned magnetic ink to selectively permit or inhibit the passage "ice of the said magnetic marking fluid through the porous membrane or printing cylinder. By this provision of an external magnetic coating, carrying a latent image thereon, this mimeograph operation may be achieved and excellent print transfers may be effected without the provision of auxiliary fluid controls or pull-out magnets whereby the overall device may be made smaller and more rugged in configuration than has been the case heretofore.

It is accordingly an object of the present invention to provide an improved printing device.

A further object of the present invention resides in the provision of an improved porous membrane for use in magnetic printing applications.

Still another object of the present invention resides in the provision of a mimeograph-type printing device utilizing a porous cylinder adapted to selectively permit or inhibit the flow of a marking fluid therethrough without the necessity of providing auxiliary fluid control structures.

A still further object of the present invention resides in the provision of a printing device which is more rugged in configuration and which may be made in smaller sizes than has been the case heretofore.

Another object of the present invention resides in an improved printing device which is less expensive to manufacture and maintain than has been the care heretofore.

The foregoing objects, advantages, construction and operation of the present invention will become more readily apparent from the following description and accompanydrawings, in which:

Figure 1 represents a printing cylinder constructed in accordance with the present invention; and

Figure 2 represents an exaggerated detail view on section 22 of Figure 1.

In accordance with the present invention, a printing cylinder may comprise a drum of porous construction having an external coating of magnetic material. This coating may be formed on the drum itself by techniques such as electro-deposition, or spraying, or it may comprise a separate membrane adapted for attachment to a supporting drum of porous construction in accordance with conventional mimeograph techniques. These particular embodiments of the present invention will be discussed more fully subsequently.

The magnetic layer thus provided may be so treated that it stores a selected pattern of magnetic gradients, representative of a latent image, thereon. Reference is made to the copending application of John Presper Eckert, Jr., and I. C. Sims, 112, Serial No. 221,362, filed April 17, 1951, for Method and Apparatus for Magnetic Printing; and to the copending application of John Presper Eckert, Jr., and John C. Sims, Jr., Serial No. 333,574, filed January 27, 1953, for: High Speed Printer. Each of these applications has been assigned to the assignee of the instant application, and they disclose apparatuses and techniques whereby printing may be effected by the utilization of magnetic principles comprising, in general, the storage of a magnetic latent image on the surface of a printing cylinder.

In accordance with the foregoing applications, such a pattern of magnetic gradients may be effected by photoscanning a sheet of material to be reproduced, thereby to derive a series of electrical signals representative of information appearing on the said sheet. Such photoscanning may be effected by an apparatus analogous to those employed in facsimile applications; and the electrical signals derived by the said photoscanning may then be coupled to a magnetic transducer or transducers mounted closely adjacent a rotatable printing cylinder having a surface of magnetic material. The said signals thereby drive the magnetic transducers to store a desired magnetic stance, by spark techniques. 'brane may then be impressed with a magnetic image by pattern, representative of information appearing on the photoscanned sheet of'material, upon the surface of'the said magnetic cylinder. The present invention contemplates the producing of asimilarpattern of magnetic "gradients upon a porous membrane of magnetic construction andthis membrane, carrying:the latent'image so-produced, 'then-cooperateswith an inking-fluidiexhibit- 'ing-magnet-ic properties.

As will appearsubsequently, the latent image'on the membrane serves to selectively agglomerate magnetic particles carried by the aforesaidink,whereby the passage maycomprise a porous cylindrical structure 11 having a porous .external coating 12exhibiting a largcplurality of;passages. 13, through which amagnetizable marking fluid or magnetic ink14 may pass selectively, in accordance with a pattern of magnetic gradientsstored in the layer 12; and the composite ink-containing cylinder or drum ma'ybemounted for'rotationona sl1aft.15. The image-receiving magnetizable coating 12 iofthe drum 1t may'comprise either a separate membrane ofporous construction placed upon the supporting cylinder 11, .orrnay in the alternative comprise a magnetic coating .o f'porous construction physically placed upon the cylinder .11. When-the separate membrane form of the present invent-ion is to be employed, such-membranes may comprise a resilient mesh-work of magnetic material, or may in the alternative comprise .a sheet of plastic coated or impregnated with magnetic oxides, and perforated,,for in- Such a magnetizable memwrapping themembrane about a recording drum of the type used in facsimile equipment and scanning the said membrane, for instance with a recording head. The said image bear'ing membrane may then be coated with a slurry of magnetic powder or a magnetic liquid appliedto the porous image-bearing surface, whereby thehigh flux concentrations existing across certainof the perforations in the membrane serve to draw the said slurryor magnetic liquid into these perforations, thus effectively closing them. The saidslurry or magnetic liquid may then be flushed from the remaining pores of the membrane by an air stream, by the action of centrifugal force, or by blotting the membrane with a magnetized roller, whereby a final semi-porous membrane is achieved, having certain pores thereof blocked by a magnetic material due to high "flux concentrations appearing thereacross, and other pores thereof unblocked due to the lack of such high flux concentrations.

The said surface 12 may also be fabricated by other techniques. Thus, such porous membranes or cylinders may be produced by forming the'cylinder 11 ofphotosensitive glass and exposing the sensitized glass to intense light through a'BenDay screen of suitable mesh. Subsequent' etching of the glass with hydrofluoric acid produces a'cylinder'having a large number of radial passages there- 'through per square inch, whereupon the outer'surface of the said etched cylinder may then be coated-with a suitable magnetizable coating 12. The etched cylinder may be:prepared for subsequent electroplating of magnetizable material thereon, for instance, by effecting a vacuum de posit of conducting material on its outer surface; or the ployed for the production of a porous cylinder having a magnetizable porous coating thereon, should not, per se, be considered limitative of the present invention, and many techniques are known and will suggest themselves to those skilled in the art whereby a suitable porous cylindrical surface of a suitable magnetic membrane may be effected.

Referring nowtoFigure 2, the'action of the printing structure shown in Figure 1 will be seen. Figure 2 is considerably exaggerated for purposes of clarity, and illustrates a section .of drum surface having a relativelysmall number of pores therein. It will be appreciated, however, that as arpractical matter, the surface will comprise several hundreds of such pores per square inch. The cylinder, as maytbe seen .in Figure.2,.ccmprises a porous supporting structure 11 and a magnetizable coating 12 defining a plurality of passages therethrough. These passages have been designated .as 20 through 32, inclusive, in theembodimentof Figure 2, and it will be seen that each passage is separated by a portion of the supporting cylinder 11 as well as by .a magnetizable portion of the coating or membrane'12. The said coating 12 may have a latent magnetic image, corresponding to materialto be reproduced, placed thereon by a'photoscanning and magnetic recording technique'suchas has been described; and in the particular illustration of Figure 2, it will beseen that magnetic segments 35, 36, 39, 42, 43, 44 and 46 have been so magnetized that they exhibit a south .pole S on the external surface thereof, while the segments 37, 38, 4%),41 and 45 have been so magnetized that they exhibit a'north pole N on the external surface thereof.

As mentioned previously, the drum contains a magnetic ink 14 and-such an-ink or marking fluid may "com- 'prise a suspension of non-magnetic pigments and finely properties. Upon rotation of the drum it), the magnetic ink tends to be forced toward the outer surface of the membrane 12 under the influence of centrifugal force. In those areas of the membrane wherein high flux concentrations exist, due to gradients arising by reason of the juxtaposition of opposite magnetic poles, the inking fluid tends to agglomerate whereby the fluid isprevented from passing'to the external surface of the printing cylinder.

In other areas, however, where no such high magnetic gradients exist, the inking fluid may pass readily;thercthrough whereby. print transfers to a recordreceivingme- .dium, such as paper 5ft, may be effected on contact.

Examining the-particular arrangement in Figure ,2, it will be seen vthat such a high magnetic gradient exists across the pores or passages 22, 24, 25, 27, 30 and 31, due to-thefact that theirnagnetic portions directly adjacent these particular pores or passages are of opposing polarities. The finely divided iron-powder suspended-in the magnetic ink 14 thus tends to agglomerate in these particular .passages, preventingthepassage of ink tothe external surface of the drum,'while the otherpassages are not so inhibited. By this arrangement, therefore, a magnetic image stored .on the surface of a drum itself, acts to permit or inhibit the passage of a markingfluid therethrough whereby a printing apparatus has been achieved which need not relyupon auxiliary fluid flow controls in effecting a desired print transfer.

While I have described. a preferred embodiment ofthe present invention, .it must be stressedthat the foregoing description is meant to beillustrativc only. ivlany-variations, certain of which have already been-suggested, will appear to those-skilled in the art, and all such variations as are in accord with the principles discussed, ;arepthere- .fore meant tofall within the scope of theappendedx'zlaims.

Having thus described my.invention,.I.claim: :1..'Inr:a printer, a...porous'membranehaving a coating of magnetizable material thereon, said coating having a pattern of magnetic gradients thereon representative of information to be reproduced, and a marking fluid, exhibiting magnetic properties, adjacent said membrane whereby said magnetic fluid is selectively inhibited from passing through selected pores in said membrane having high magnetic gradients adjacent thereto.

2. The printer of claim 1 wherein said porous membrane comprises the external surface of a cylindrical printing drum, said magnetic marking fluid being disposed within said drum, and a print receiving medium contiguous with the external surface of said drum.

3. In a printer, a porous membrane of magnetizable material having a latent image thereon comprising a pattern of magnetic gradients representative of information to be reproduced, said pattern of gradients comprising unlike magnetic poles adjacent certain of the pores in said membrane and like magnetic poles adjacent other in said membrane and like magnetic poles adjacent other of the pores in said membrane, and a magnetic marking fluid disposed adjacent one side of said membrane, whereby said fluid is magnetically retained in those pores of said membrane having unlike magnetic poles adjacent thereto while said magnetic fluid readily passes through the pores of said membrane having like magnetic poles adjacent thereto thereby to effect a selective passage of marking fluid through said membrane in accordance with said latent image.

4. The printer of claim 3 wherein said marking fluid comprises a suspension of unmagnetized particles of magnetic material in a liquid vehicle.

5. The printer of claim 4 wherein said membrane comprises the external surface of a fluid permeable printing cylinder, said marking fluid being disposed on the interior of said cylinder, and a print receiving medium contiguous with said external surface of said printing cylinder.

6. The printer of claim 5 wherein said external surface of magnetizable material comprises a removable magnetic membrane supported by said printing cylinder.

7. In a printer, a printing cylinder mounted for rotation, said printing cylinder being of porous construction and having an external surface of porous magnetizable material, said external surface having a pattern of magnetic gradients stored thereon representative of information to be reproduced, a magnetic marking fluid disposed within said printing cylinder for selective passage through said cylinder and surface in accordance with said stored pattern of magnetic gradients, and a print receiving medium contiguous with said external surface.

8. The printer of claim 7 wherein said marking fluid comprises a mass of finely divided magnetic particles in liquid suspension, whereby said magnetic particles agglomerate in those pores of said external magnetizable surface having relatively high potential gradients thereacross.

9. In a printer, a porous membrane of magnetizable material having a latent image thereon comprising stored magnetic gradients representative of information to be reproduced, fluid passage control means comprising magnetic particles selectively retained within selected pores of said membrane in accordance with said stored magnetic gradients, a marking fluid adjacent one side of said membrane, and a print receiving medium adjacent the other side of said membrane, whereby said marking fluid is inhibited from passing through those pores of said membrane having said magnetic particles retained therein, said marking fluid passing through pores of said membrane, not so inhibited, to said print receiving medium.

10. The printer of claim 9 wherein said porous membrane comprises an external coating on a porous printing cylinder.

11. The printer of claim 10 wherein said magnetic particles are in suspension in said marking fluid.

12. The printer of claim 9 wherein said porous membrane is disposed on the external periphery of a cylindrical printing drum.

13. The printer of claim 12 wherein said magnetic particles comprise finely divided ferromagnetic material in suspension in said marking fluid, said marking fluid being disposed on the interior of said printing drum.

14. In a printer, a porous member having a magnetizable surface adapted to contact a print receiving medium, said surface having a pattern of magnetic gradients stored thereon representative of information, a marking substance exhibiting magnetic properties in contact with the surface of said member opposite the surface adapted to contact the print receiving medium, whereby said marking substance is selectively inhibited from passing through the pores in said member having high magnetic gradients adjacent thereto.

15. In a printer, a porous member having a coating of magnetizable material thereon, said coating having a pattern of magnetic gradients thereon representative of information to be reproduced, and a marking medium exhibiting magnetic properties adjacent said member whereby said marking medium is selectively inhibited from passing through selected pores in said member having high magnetic gradients adjacent thereto.

16. Printing apparatus comprising a porous member including a magnetizable surface having impressed thereon a pattern of magnetic gradients representing information to be printed, and a magnetic printing medium adjacent said member, said member being pervious to said medium in areas of said surface having low magnetic gradients and impervious to said medium in areas of said surface having high magnetic gradients.

No references cited. 

